1. Field of the Invention
This invention relates to a peroxide curing ethylene-propylene rubber composition.
In the present invention, since an ethylene-propylene non-conjugate diene tertpolymer is used as the ethylene-propylene rubber, the ethylene-propylene rubber will be referred to hereinafter as "EPDM".
Particularly, this invention elates to an EPDM composition which is capable of obtaining not only the heat resistance particularly required for automobile radiator hoses and other rubber products, but also equivalent physical properties in original state and oil resistance to those of the rubber products formed of a sulfur curing EPDM.
In the following description, the compositions will be expressed by proportions of components in weight.
The abbreviations to be used hereinbelow will be defined as follows.
EPDM --Ethylene-propylene non-conjugated diene terpolymer: A composite obtained by combining ethylene and propylene as main components with a minor amount of a non-conjugated dienes thereby incorporating a double bond in the side chain of the molecule and consequently rendering the composite curable with sulfur. The non-conjugated dienes which are usable herein include ethylidene norbornene and cyclopentadiene, for example.
ML.sub.1+4 (100.degree. C. ) --Unit of Mooney viscosity: The scale reading of the tester using a large disc (L) obtained after one minute's preheating of the disc plus four minutes rotation of the disc.
2. Description of the Prior Art
The EPDM composition excels in weatherability, heat resistance, hot water resistance, steam resistance, etc. and, consequently, it is extensively used for radiator hoses. Conventional sulfur cured EPDM compositions have superior physical properties in original state (such as tensile strength, etc.) and oil resistance, over conventional peroxide cured EPDM compositions.
Meanwhile, the conventional peroxide cured EPDM composition generally Excel over the sulfur cured EPDM compositions in terms of heat resistance, hot water resistance, etc.
The radiator hose has recently come to demand heat resistance, hot water resistance, etc. more than ever before. Therefore, an attempt has been made to use the conventional peroxide cured EPDM compositions as a material for the hose.
Unfortunately, the conventional peroxide cured EPDM compositions do no give equivalent physical properties in original state and oil resistance to conventional sulfur cured EPDM composition.